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2023 OMIG Abstract
Purpose: To evaluate the efficacy of ultraviolet-C beam against susceptible and multidrug resistant Pseudomonas aeruginosa using in vitro and in vivo experiments.
Methods: For in vitro evaluation, two clinical isolates of P. aeruginosa obtained from corneal scraping of patients with microbial keratitis were taken, one multidrug resistant (MDR) isolate that was susceptible to ceftazidime and the other that was susceptible to all antibiotics. For both isolates the in vitro experiment consisted of lawn culture of 108 cfu/ml of bacterial suspension on Mueller-Hinton agar, followed by UVC (265 nm, 1.93 mW/cm2) exposure using delivery system (Photon-Therapeutics) for variable duration of 5, 10, 15, and 30 seconds. The plates were incubated for 48 hours at 37o C at the end of which inhibition of growth was graded by observation of clarity (+, ++, +++) at each time point. The in vivo experiment included a murine model (C57BL mice) of keratitis performed in two parts. Two sets of mice (n=24 each) were infected with either susceptible P. aeruginosa or the MDR strain. The groups were divided into four subgroups (6 each): a) untreated control, b) UVC exposure (after 4 hours of inoculation) delivered daily (15 seconds exposure/ 2 times x 4 hourly/2 days), c) ciprofloxacin 0.3% eye drop (twice daily/2 days), d) ciprofloxacin 0.3% or ceftazidime 5% (for MDR) two hourly. All the eyes were evaluated clinically under operating microscope by a masked (to the groups) observer at 24 and 48 hours. After 48hrs, mice were euthanized; both the eyeballs were enucleated and subjected to microbiological and histopathological evaluation.
Results: Maximum inhibition of +++ was obtained for both isolates at 30 seconds exposure, while it was ++ at 15 seconds; the time used for exposure in the in vivo experiment. In murine model, compared to control eyes the UVC treatment significantly reduced the over-all clinical severity (p<0.05) of infection measured by significant decline in lid swelling (p<0.01), discharge (p<0.05), corneal haziness (p<0.01), and stromal infiltrate (p<0.01) in both groups. The clinical effect of UVC and antibiotics, to which the organisms were susceptible (ciprofloxacin/ceftazidime), were comparable. This correlated well microbiologically with no evidence of growth of bacteria from homogenized eye balls from the UVC and antibiotic treated eyes.
Conclusions: UVC 265 nm shows a time-dependent in vitro bactericidal effect which correlated with in vivo murine model in both susceptible and MDR P. aeruginosa. We recommend the use of this technique for future treatment stand alone and quicker option for managing bacterial keratitis especially those caused by MDR bacteria.
Disclosure:
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